An example of a conventional air conditioning apparatus includes a separate type air conditioning apparatus in which a heat source unit and a utilization unit are connected via a connection pipe to constitute a refrigerating circuit. Examples of the separate type air conditioning apparatus include a room air conditioner and a package air conditioner.
An example of a refrigerating cycle apparatus in which a heat source unit and a utilization unit are integrated is an air-cooling heat pump chiller. In this refrigerating cycle apparatus, if a connecting portion such as a pipe is not fastened sufficiently, the refrigerant may leak gradually through a gap in the fastening portion of the pipe or the like over a long-term use of the refrigerating cycle apparatus.
Damage to the pipe may lead to an unexpected refrigerant leakage. The refrigerant leakage causes a decrease in air conditioning capacity and damage to the constituent devices. In a serious case, the refrigerating cycle apparatus may have to be stopped for safety reasons.
If the refrigerating circuit is charged with the refrigerant excessively, the liquid refrigerant runs under a pressure in the compressor for long period of time, leading to a failure. Therefore, from the viewpoint of the quality and improving the maintenance easiness, it is desirable that a function is provided that determines the excess/shortage of the refrigerant amount by calculating the amount of refrigerant charged in the refrigerating cycle apparatus.
To cope with these problems, conventionally, a method has been proposed, of determining the excess/shortage of the refrigerant amount by calculating the refrigerant amounts in the respective elements which constitute the refrigerating circuit, by using an estimation formula obtained by regression analysis on operation state amounts which are highly correlated to each other in the respective elements (see, e.g., patent literatures 1 to 3).